Regenerative counter-propeller for marine vessels



R. W. BIRKETT. REGENERATIVE COUNTERPROPELLER FOR MARINE VESSELSf APPLICAIION HLED JAN-24,1920- 1921., 2 SHEETS-SHEET l- Patented Aug. 9

INVEHTQR.

R. W. BIRKETT.

REGENERATIVE COUNTER PROPELLER FOR MARINEVESSELS. v

APPLICAIION FILED JAN-24.1920.

Patented Aug. 9, 1921..

wires Specification of Letters Patent.

- RALPH wnirnrinan BIRKETT, or screen, nuenaun.

REGENERATIVE COUNTER-PROPELLER FGR MARINE VESSELS.

Patented ate. a, 1921.

Application filed January 24, 1920. Serial No, 353,851. I

' Surrey, England, have invented new and useful Improvements in Regenerative Counter-Propellers for Marine'Vessels, of which the following is a specification.

This invention relates to devices of the order of auxiliaiyattachments employed in conjunction with screw-propellers for marine craft, which devices have been generically known as regenerative propellers, or counter propellers or stator propellers.

Such devices are based uponthe principle of intercepting or deflecting the currents of water outflowing from a revolving screwpropeller, witha view to increasing the efiiciency of thrust or propulsive effect.- lhey consist primarily of blades 'or deflectors, placed around or in the wake of the propeller, and said blades are usually fitted in a surrounding and supporting casing of tubular form, or are built in a sort of tunnel construction formed in the superstructure of the vessel.

My invention however, differs from such known types, inasmuch as its blades, being stationary, are disposed radially and are mainly supported by a fixed central hub,- which hub may in turn be partly supported by an extension of the end of the propeller shaft, or may beattached to the stern frame, while the outer ends of some of the blades may be attached to, or stayed from the superstructure of the vessel. The construction is thus quite open, and there are noencircling casings or tunnel-tubes, thereby eliminating such frictional surfaces, which have been found detrimental in practice. v

It is well understood that the angle, in relation to the. axis of the propeller and direction oftravel of the vessel at which such guiding blades are set, must be carefully selected. Heretofore reliance has been placed upon calculations to determine this angle, or it has been assumed that it must be such that the plane of the reacting surfaces of the counter-propeller blades must coincide approximately to the angle of outflow of fluid from the revolving propeller blades. The angle of the blades beingthus determined, the counter-propeller has been so constructed, that the setting of its blades has been unalterable.

As is well known however, the characteristics of the best and most efficient screw propeller forany vessel, canonly be approximately arrived at by calculation, and its final determination is a matter for experimental trial; so that it is often found neces- 'sary to run trials with several differing designs of propellers, before the most succes- I ful for an individual vessel can be finally selected. 7

Any such necessary modifications will usually involve a modification of the angle of the propeller blades, and when the propeller V is to run in conjunction with a counter-propeller, such modification renders necessary a corresponding modification of the angle of the blades of the counter-propeller. Thus in existing practice, it is necessary when fitting a new propeller, also to provide an entirely new counter propeller to conform to its characteristics, if the best effects are to be obtained from the combination.

Further, the best degree of deflection from the angle of axial outflow from the propeller by the angular setting of the counterpropeller surfaces, may differ from the angle which was assumed, (as this may be infiuenced to some extent by the pitch and speed of revolution of the propeller) in which case also it becomes desirable to change the angle of the counter-propeller blades, and this can only be done by entirely reconstructing or providing a new counterpropeller fitting.

in order to deal more easily with such varying conditions therefore, my present invention provides, forthe first part, for the construction of a hub, or center, and the blades of a counter-propeller, in such manner, that the angle of the reacting surfaces of said blades, in relation to the axial line of the propeller shaft and the direction of travel of thevessel, obtain the highest propulsive efficiency of the combination, of a screw propeller and a counter-propeller, as described herein.

Secondly, my invention further provides, that the said hub, instead of being rigidly fixed as described, may alternatively be pivoted, or hinged, somewhat in the manner of a steering rudder, in order that the counterpropellermay perform an additional function, in steering, or assisting the steering,

of avessel, by divertingaiid directing the propulsive et issuing from the screw-prois variable, in order to peller, the jet being then influenced by the counter-propeller blades to flow aft in a port 1 or starboard'angle.

My invention is. applicable toan-y vessel obtaining its "propulsion "from screw-propellers.

In the accompanying drawings Figurev 1. is a side-elevation of the stern}:

portionof a essel, showing its screw-propeller and the first form of a fixed counterpropeller, as I provided by thls. invention.

' Fig.2. is anend view of similar counter propellersas, adapted to twin-screw vessels.

Fig: 31 fis side-elevation" of 'a counter "propeller in the second form, adapted to a single-screw vessel, and pivoted to operate for steering purposes.

"Fig. 1. is'anend-view of thecombination shown inFig. 3.

' Fig. is a plan-view of the same.

Fig. .6. 18 a plan-view of the boss or hub of the counter propellers, showing (sectionally) one of its blades, and the bracketlug on the boss and .rnanner of attaching the blades'to same. 7 I

s Fig. 7; "is an enlarged view of a portion of r Fig. 6-. showing the adjustable serrated liner single-screw vessels, when it is convenient to secure the hub 1. to thesternpostQ. ust.

or distancepiece interposed to determine the angle of the blade setting. L"

' he construction in Fig. 1. is adapted for aft of the propeller 3. w The hub 1;.may have a recess forrned in its after-end: (asshown in Fig. 6.) to -fit it around'the .sternfraine 2.

'Upon' the periphery oztjhubl. are cast, or

otherwise formed, the lugs or brackets 4. The plane surfaces or faces of these lugs are straight, but the lugs areset at a slight angle to the axial center-line of the propeller shaft. The blades 5'. of the counter-propeller radiate from Land are secured at their inner ends to lugs 1., by meansoi removable belts or screws, but are not permanently riveted thereto. T he outer ends of some of the blades may be extended and secured to the superstructure as shown at 10., to serve as supporting stays for the counter-propeller fitting;

Referring to Figs. 6(and 7., the inner sur- I faces of brackets 1; may be serrated as shown, to correspond with serrations in the liners 6., the boltholes in which inaycon ve'niently be slotted to "facilitate adjustment.

The wedge-shaped. distance-pieces 6. are interposed between lugs 4c. andfblades 5. and their outer "faces are curved "suitably to fit thecurvedsurfaces of the said blades.

'Thus, by varying the distance-of insertion 01 6., or alternatively by fitting liners of differing thickness or taper, the'angle of the settingv of blades 5. with relation to the axial center-line of propeller 3.,- may be varied as desired. H

- counter-propeller fitting is held against rotation, and inthe types shown in Ti'gs. 1. and 2., is not intended to havev any I working movement. I

I Should'the c-urvatureqotblades .5. be considerable, taper liners of suitable shape would also be fitted'as'at 84in Fig. 6.

My design is equally adaptable to multiple- --screw vessels, and in Fig. 2., I have indicated one method of fitting, for example, toa twin screw vessel; .The hubs 1. insuch cases. will be bored out to receive the end of an exten: sion of the propellershaft' as indicated at 9. in Fig. '1. The details of attachment of blades to hubs 1. Willbe similarto Fig. 6.,and some of the blades being attached to the hull asat 10., will give ladditio-nal sup; port and prevent thecounter-propellerro tating.

In the case of large counter propellers,

I Qiurther staying oi": the; blades to each other 3. is shown by thearrow in Fig.2., and it willbe observed that each radiating bladef is slightly bent, or curvedtowardthe tip in a direction opposlte to theirotation of an propeller. This method of construction 18 sometimes used, but is notessential, and

is not claimed as a part of thisinyention. T have shown an alternative construction with stra ght blades in Fig. 1 which can be equally used in counter-propellersofthe typeset Fig. 1.0-1 Fig. 2.

Another modification of my invention is shown in Figs. 8., 4:; -and 5, which could be adopted in suitable cases, whereby an addi tional function can be performed by counterpropellers made hereunder.

In thisit'orin, while the counter-propeller blades might be made'either'fixed'oradjustableu'pon the hub, as inF ig. 1. and Fig. 2.,

the details of support for the hub would be differently arranged. Referring to Fig. 3., it will be seen that the counter-propeller is then not supported by the: endof the screwpropeller shaft, as in E ig. 1., but that'a space is allowed between the propeller '16. andithe counter-propeller fitting. 'Abaft thepropeller 16. fixed sternpost 18. is shown, which might be specially provided, or, (if the ordinary form of rudder is. dispensed, with) the usual position for theirudder-ipost can be utilized. Around this stern'-post13., a;hol-

low shaft or tube 14. isifitt'ed. 'Thepjost'f13.

and the .tubularshaft 14., 'passfjvertically through hub 12., but 141 is'conneetedtofil2.

and forms its axle, which is revoluble around 13. Thus, if 14. be extended upward through the deck of the vessel and be connected to a tiller or other steering-gear, then a partial revolution of 14. in either direction, will have the effect of turning the blades 15. of the counter-propeller to any desired port or starboard angle. This application of the counter-propeller will enable the vessel being steered by deflection of the outflowing currents from the propeller blades 16, and will give a powerful steering effect, that can be utilized either alone, or in conjunction with an ordinary rudder. It will in fact, constitute in itself a multiple-bladed rudder, steering directly by the power of the propulsive stream, instead of the secondary reaction of the ordinary rudder, while securing also the beneficial action of the counter-propeller in. regenerating the otherwise lost energy of the rotatory motion ofthe propeller currents.

From the foregoing and by'reference to the attached drawing it will be obvious that, whenthe main propellers (3. in Figs. 1. and 2., or 16. in Fig. 3.) are revolved, the outflowing currents of water from their blades, which would normally have a movement in part of circular or spiral character, will as regards such rotatory motion, be broken up, and diverted to flow in an axial direction, by the reactive effect of the angularly disposed blades of the counter-propeller, as shown in sectional plan in Fig. 5. For the reasons previouslystated, the angle of incidence of the blades (5. or 15.) has an important influence upon the efiiciency of the counter-propeller, and the best angle cannot be absolutely predetermined. As described therefore, one object of my present invention is to provide means, whereby the angular position of the said blades, may be provided to be alterable and adjustable, instead of (as in previous devices of the kind) being fixed and unalterable, in relation to the angle of the propeller blades (3. or 16.). By this provision, the best possible relationship of the angular settings of the revolving propeller blades and the stationary regenerating blades, may be ascertained by actualtrials of the vessel, before a permanent, or semi-permanent, fixing of the position of the said counter-propeller blades is decided upon. This object is equally attained by any of the figures shown, and also a secondary object, namely, steering or assisting the steering of a vessel, is additionally attained, when the modified arrangement shown in Fig. 3. is adopted.

It is to be understood, further, that the methods above described, and shown in the drawings, are given by way of example only, and that numerous other means may be devised for effecting the objects or combinations stated, all of which means will fall within the scope of this invention.

WVhat I claim is 1. In a device of the class described, in combination with a screw propeller, a central hub supported from the structure of a vessel and arranged centrally behind the said screw propeller, a plurality of stationary detachable blades radiating from said central hub, and disposed with their forward edges facing approximately in the direction of travel and secured to said hub and to the structure, with means for readjusting the angular disposition of their plane surfaces to any desired angle in relation to the axial line of the shaft of the said screw propeller.

2. In a regenerative propeller of the class described, in combination with a screw propeller, a central hub having brackets with straight plane faces on its outer surface, intermediary liners, said liners having one surface straight and fitted against said bracket faces and their outer surface curved adaptably to the curved surfaces of detachable radiating blades attached to said hub by bolting through said liners and brackets, with means for adjustably securing said blades with their plane surfaces set in any desired angular position in relation to the axial line of the shaft of the said screw propeller.

3. In a device of the class described, in combination with a screw propeller, a central hub, a plurality of radiating blades attached to said hub and disposed with their plane surfaces approximately parallel to the direction of travel, said hub and blades arranged centrally behind said screw propeller and supported by a vertical tubular axle shaft, said tubular shaft fitted around a vertical solid shaft fixed in the stern structure of a vessel, said axle shaft passing through the forward end of hub and keyed to same and supported at its lower end in a footstep bearing and adapted to be partially revolved for steering purposes'so as to turn the said hub and attached blades to port and starboard angles of the vessels course.

Dated this sixth day of January, 1920.

RALPH WHITEHEAD BIRKETT.

Witnesses:

DOROTHY M. LESSETT, ARTHUR W. LUNDRIDGE. 

